1. Field of the Invention
The present invention relates to a method for activating a fuel cell having an electrolyte membrane containing a solid polymer, and more specifically to a method for activating a fuel cell, the method being capable of judging an activation completion timing.
2. Description of the Related Art
As is well known, a fuel cell having an electrolyte membrane containing a solid polymer is referred to as a solid polymer electrolyte fuel cell. The fuel cell contains a membrane-electrode assembly, which is formed by sandwiching the electrolyte membrane between an anode and a cathode.
This type of the fuel cell is subjected to a treatment for achieving a sufficient power generation performance. For example, before the fuel cell is practically operated, the fuel cell is subjected to a preliminary operation for supplying a sufficient amount of moisture to the electrolyte membrane (i.e. aging). For example, in Japanese Laid-Open Patent Publication No. 2005-243245, the applicant has proposed an aging method containing the steps of gradually increasing the output current of the fuel cell to a predetermined upper limit value and thereafter keeping the output current at the upper limit value.
Furthermore, Japanese Laid-Open Patent Publication No. 2008-204799 proposes an activation method, wherein a highly crystalline carbon black having an Lc value of 5 or more is used as a carrier for a catalyst included in electrode catalyst layers of the anode and the cathode, and a voltage periodically varying within a range of 1.0 to 1.5 V is repeatedly applied between the anode and the cathode.